The Tube Cleaning Hollow Drill is 3/16" (4.8mm) diameter x 4' (1.2m) long. It is used to drill into mineral scale and other deposits in severely, or completely clogged tubes - allowing a lead hole for other tools to finish the cleaning job. Integrated water flows through hollow shafts and flushes deposits as they are generated, for a better cleaning performance. For use with PSM-500 Tube Cleaner Drill.